Jemmy is a JavaTM library that is used to create automated tests for Java GUI applications. It contains methods to reproduce all user actions which can be performed on Swing/AWT components (i.e. button pushing, text typing, tree node expanding, ...). Jemmy can be used with any test harness (such as XTest, for example). The programmer simply has to adopt his tests to the harness requirements. It also can be used to create a demo for Java GUI applications. It's pretty effective for automating demo to show how an application works, showing comments during the process, and then says: Hey! Now, go ahead and play with the opened windows! This is a real application we are presenting!
Jemmy really is a NetBeansTM independent module, you can use it separately as well as together with the NetBeans IDE.